[antlr-interest] Difference between negative literal and negative fragment ?

Pururav Thoutireddy pururav at gmail.com
Fri Jan 20 13:43:12 PST 2012


Hi,

Is there a way of generating c/c++ code corresponding to the formula
written in the given grammar I.e code generation from sat tree.

Thanks
Puru
On Jan 20, 2012 12:33 PM, "Peter Boughton" <boughtonp at gmail.com> wrote:

> See this example lexer grammar:
>
>        fragment START_TAG    : '<';
>        fragment WORDCHAR     : 'a'..'z' | 'A'..'Z' | '0'..'9' | '_';
>
>        TAG_START : START_TAG WORDCHAR+ { pushMode(IN_TAG); };
>
>        ANY_GENERAL : ~START_TAG+;
>        // ANY_GENERAL : ~'<'+;
>
> Using the first ANY_GENERAL rule, it consumes everything.
>
> Swapping for the second ANY_GENERAL rule, it works as intended.
>
> I don't understand why they are not doing the same thing?
>
> Are there any other situations where using a literal over a fragment
> will have different behaviour?
>
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